System and method for generating and displaying contours

ABSTRACT

A system and method for generating and displaying contours. In some embodiments, the method includes: generating a respective first axial contour, of a plurality of first axial contours, for each of a first plurality of axial slices, the first axial contours defining a surface of a first volume, a first axial slice of the first plurality of axial slices including a first target point; generating a first sagittal contour in a first sagittal slice through the first target point; generating a respective second axial contour, of a plurality of second axial contours, for each of a second plurality of axial slices including the first axial slice, the second axial contours defining a surface of a second volume, a first slice of the first plurality of axial slices including a second target point; and generating a second sagittal contour in the first sagittal slice.

FIELD

One or more aspects of embodiments according to the present disclosurerelate to medical imaging, and more particularly to a system and methodfor drawing and displaying contours around one or more lesions in amedical imaging scan.

BACKGROUND

Medical imaging scans, such as magnetic resonance imaging (MRI) scansand computerized axial tomography (CT or CAT) scans are procedures thatmay be used to obtain information about the internal structure of anobject, such as a patient.

In a medical imaging scan, a lesion, such as a cancerous portion of anorgan, may have a different density than surrounding healthy tissue. Itmay be useful to determine a contour corresponding to the boundarybetween cancerous tissue and healthy tissue, so that, for example, thevolume of a cancerous region may be estimated.

Drawing such a contour manually, e.g., by a radiologist operating acomputer, may be time-consuming and imprecise, and the repeatability ofsuch a method may be poor. Thus, there is a need for an improved systemand method for generating contours in medical imaging scans.

SUMMARY

According to an embodiment of the present disclosure, there is provideda method for analyzing scan data, the method including: generating arespective first axial contour, of a plurality of first axial contours,for each of a first plurality of axial slices, the first axial contoursdefining a surface of a first volume, a first axial slice of the firstplurality of axial slices including a first target point; generating afirst sagittal contour in a first sagittal slice through the firsttarget point, the first sagittal contour being in the surface of thefirst volume; generating a respective second axial contour, of aplurality of second axial contours, for each of a second plurality ofaxial slices including the first axial slice, the second axial contoursdefining a surface of a second volume, a first slice of the firstplurality of axial slices including a second target point; andgenerating a second sagittal contour in the first sagittal slice, thesecond sagittal contour being in the surface of the second volume.

In some embodiments, the method further includes displaying: the firstaxial slice; the first axial contour of the first axial slice, overlaidon the first axial slice; the second axial contour of the first axialslice, overlaid on the first axial slice; the first sagittal slice; thefirst sagittal contour, overlaid on the first sagittal slice; and thesecond sagittal contour, overlaid on the first sagittal slice.

In some embodiments, the displaying of the first sagittal slice, thefirst sagittal contour, and the second sagittal contour includes:displaying the first sagittal contour in a first color, and displayingthe second sagittal contour in a second color, different from the firstcolor.

In some embodiments, the method further includes generating a torsocontour in the first axial slice, the first axial slice being a slice ofan imaging scan of a patient, the torso contour corresponding to theboundary, in the first axial slice, of the torso of the patient.

In some embodiments, the generating of the torso contour includes:calculating a first plurality of maximum values, each of the maximumvalues being the maximum value within a respective slice of a thirdplurality of axial slices, the third plurality of axial slices includingthe first plurality of axial slices and the second plurality of axialslices; calculating a first threshold based on the median of the maximumvalues; and defining a first rectangle having: a left edge at a firstpeak, in order, of two or more horizontal peaks exceeding the firstthreshold in a central row of a central slice of the third plurality ofaxial slices; a right edge at a last peak, in order, of the two or morehorizontal peaks; a top edge at a first peak, in order, of two or morevertical peaks exceeding the first threshold in a central column of thecentral slice; and a bottom edge at a last peak, in order, of the two ormore vertical peaks.

In some embodiments, the generating of the torso contour furtherincludes: calculating a second plurality of maximum values, each of thesecond plurality of maximum values being the maximum value within thefirst rectangle in a respective slice of the third plurality of axialslices, and calculating a second threshold based on the median of thesecond plurality of maximum values.

In some embodiments, the generating of the torso contour furtherincludes finding a boundary of a region exceeding the second threshold.

In some embodiments: the scan data is computerized tomography scan data;the generating of the torso contour further includes: calculating ahorizontal moving sum along the central row; calculating a verticalmoving sum along the central column; and defining a second rectanglehaving: a left edge at a first value, in order, of the horizontal movingsum, exceeding a third threshold; a right edge at a last value, inorder, of the horizontal moving sum, exceeding the third threshold; atop edge at a first value, in order, of the vertical moving sum,exceeding the third threshold; and a bottom edge at a last value, inorder, of the vertical moving sum, exceeding the third threshold; andthe region is within the second rectangle.

According to an embodiment of the present disclosure, there is provideda non-transitory computer readable medium, the non-transitory computerreadable medium storing instructions that, when executed by a processingcircuit, cause the processing circuit to: generate a respective firstaxial contour, of a plurality of first axial contours, for each of afirst plurality of axial slices, the first axial contours defining asurface of a first volume, a first axial slice of the first plurality ofaxial slices including a first target point; generate a first sagittalcontour in a first sagittal slice through the first target point, thefirst sagittal contour being in the surface of the first volume;generate a respective second axial contour, of a plurality of secondaxial contours, for each of a second plurality of axial slices includingthe first axial slice, the second axial contours defining a surface of asecond volume, a first slice of the first plurality of axial slicesincluding a second target point; and generate a second sagittal contourin the first sagittal slice, the second sagittal contour being in thesurface of the second volume.

In some embodiments, the instructions further cause the processingcircuit to display: the first axial slice; the first axial contour ofthe first axial slice, overlaid on the first axial slice; the secondaxial contour of the first axial slice, overlaid on the first axialslice; the first sagittal slice; the first sagittal contour, overlaid onthe first sagittal slice; and the second sagittal contour, overlaid onthe first sagittal slice.

In some embodiments, the displaying of the first sagittal slice, thefirst sagittal contour, and the second sagittal contour includes:displaying the first sagittal contour in a first color, and displayingthe second sagittal contour in a second color, different from the firstcolor.

In some embodiments, the instructions further cause the processingcircuit to generate a torso contour in the first axial slice, the firstaxial slice being a slice of an imaging scan of a patient, the torsocontour corresponding to the boundary, in the first axial slice, of thetorso of the patient.

In some embodiments, the generating of the torso contour includes:calculating a first plurality of maximum values, each of the maximumvalues being the maximum value within a respective slice of a thirdplurality of axial slices, the third plurality of axial slices includingthe first plurality of axial slices and the second plurality of axialslices; calculating a first threshold based on the median of the maximumvalues; and defining a first rectangle having: a left edge at a firstpeak, in order, of two or more horizontal peaks exceeding the firstthreshold in a central row of a central slice of the third plurality ofaxial slices; a right edge at a last peak, in order, of the two or morehorizontal peaks; a top edge at a first peak, in order, of two or morevertical peaks exceeding the first threshold in a central column of thecentral slice; and a bottom edge at a last peak, in order, of the two ormore vertical peaks.

In some embodiments, the generating of the torso contour furtherincludes: calculating a second plurality of maximum values, each of thesecond plurality of maximum values being the maximum value within thefirst rectangle in a respective slice of the third plurality of axialslices, and calculating a second threshold based on the median of thesecond plurality of maximum values.

In some embodiments, the generating of the torso contour furtherincludes finding a boundary of a region exceeding the second threshold.

In some embodiments: the scan data is computerized tomography scan data;the generating of the torso contour further includes: calculating ahorizontal moving sum along the central row; calculating a verticalmoving sum along the central column; and defining a second rectanglehaving: a left edge at a first value, in order, of the horizontal movingsum, exceeding a third threshold; a right edge at a last value, inorder, of the horizontal moving sum, exceeding the third threshold; atop edge at a first value, in order, of the vertical moving sum,exceeding the third threshold; and a bottom edge at a last value, inorder, of the vertical moving sum, exceeding the third threshold; andthe region is within the second rectangle.

According to an embodiment of the present disclosure, there is provideda system for generating a view of an interior of an object, the systemincluding: a scanner for scanning the object; a processing circuit; anda display, the processing circuit being configured to: generate arespective first axial contour, of a plurality of first axial contours,for each of a first plurality of axial slices, the first axial contoursdefining a surface of a first volume, a first axial slice of the firstplurality of axial slices including a first target point; generate afirst sagittal contour in a first sagittal slice through the firsttarget point, the first sagittal contour being in the surface of thefirst volume; generate a respective second axial contour, of a pluralityof second axial contours, for each of a second plurality of axial slicesincluding the first axial slice, the second axial contours defining asurface of a second volume, a first slice of the first plurality ofaxial slices including a second target point; and generate a secondsagittal contour in the first sagittal slice, the second sagittalcontour being in the surface of the second volume.

In some embodiments, the processing circuit is further configured todisplay: the first axial slice; the first axial contour of the firstaxial slice, overlaid on the first axial slice; the second axial contourof the first axial slice, overlaid on the first axial slice; the firstsagittal slice; the first sagittal contour, overlaid on the firstsagittal slice; and the second sagittal contour, overlaid on the firstsagittal slice.

In some embodiments, the displaying of the first sagittal slice; thefirst sagittal contour; and the second sagittal contour includes:displaying the first sagittal contour in a first color, and displayingthe second sagittal contour in a second color, different from the firstcolor.

In some embodiments, the processing circuit is further configured togenerate a torso contour in the first axial slice, the first axial slicebeing a slice of an imaging scan of a patient, the torso contourcorresponding to the boundary, in the first axial slice, of the torso ofthe patient.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, aspects, and embodiments are described in conjunction with theattached drawings, in which:

FIG. 1 is a block diagram of a system for performing and analyzing amedical imaging scan, according to an embodiment of the presentdisclosure;

FIG. 2 is a view of an axial slice of an imaging scan, according to anembodiment of the present disclosure;

FIG. 3A is a view of an axial slice of an imaging scan, according to anembodiment of the present disclosure; and

FIG. 3B is a view of a sagittal slice of an imaging scan, according toan embodiment of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of exemplary embodiments of asystem and method for generating and displaying contours provided inaccordance with the present disclosure and is not intended to representthe only forms in which the present disclosure may be constructed orutilized. The description sets forth the features of the presentdisclosure in connection with the illustrated embodiments. It is to beunderstood, however, that the same or equivalent functions andstructures may be accomplished by different embodiments that are alsointended to be encompassed within the scope of the disclosure. Asdenoted elsewhere herein, like element numbers are intended to indicatelike elements or features.

A computerized axial tomography (CAT) scan is a procedure in which anobject (e.g., a patient) is illuminated from several directions withpenetrating (e.g., X-ray) radiation from a radiation source, and a scanimage of the transmitted radiation is formed, in each instance, by adetector, to form a plurality of scan images, each of which may berepresented as a two-dimensional array. The radiation may be attenuatedat different rates in different kinds of matter; accordingly, each pointin each image may correspond to a transmitted radiant intensitydepending on the attenuation rates of the compositions of matter on thepath along which the radiation traveled from the radiation source to thedetector. From the combination of scan images, raw scan data, e.g., athree-dimensional model of the “density” of the object (which may bereferred to as a three-dimensional scan data array) may be formed.

As used herein, the “density” within an object is any characteristicthat varies within the object and that is measured by the medicalimaging scan. For example, with respect to CAT scans, the “density” mayrefer to the local rate of attenuation of the penetrating radiation, andwith respect to MRI scans, the “density” may refer to the density ofatoms having a nuclear resonance at the frequency of the probe radiofrequency signal, in the presence of the magnetic field being applied.

Although some examples are discussed in the present disclosure in thecontext of CAT scans or MRI scans of a human patient, the disclosure isnot limited thereto, and in some embodiments other kinds of scansproviding three-dimensional density data such as positron emissiontomography scans, or scans of objects other than human patients, may beprocessed in an analogous fashion. In the case of other kinds of scans,density may be defined accordingly; in the case of a positron emissiontomography scan, for example, the density may be the density of nucleithat decay by beta plus emission. As used herein, the term “object”includes anything that may be scanned, and encompasses withoutlimitation human patients, animals, plants, inanimate objects, andcombinations thereof.

When the object being imaged is a human patient (or other livingobject), a contrast agent may be used (e.g., injected into or ingestedby the patient) to selectively alter the density of some tissues. Thecontrast agent may for example include a relatively opaque substance(i.e., relatively opaque to the penetrating radiation). The density oftissue containing the contrast agent may be increased as a result, andit may be increased to an extent that depends on the concentration ofcontrast agent in the tissue. The concentration of the contrast agentmay initially increase in the tissue, and then gradually decrease again,and the density of the tissue may similarly increase initially and, thendecrease.

FIG. 1 shows a block diagram of a system for performing a scan andprocessing and displaying the results, according to one embodiment. Thesystem includes a scanner 110, a processing circuit 115 (described infurther detail below), a display 120 for displaying images, or sequencesof images in the form of a movie (or “video”), and one or more inputdevices 125 such as a keyboard or mouse, that an operator, or “user”(e.g., a radiologist) may use to operate the system, and to setparameters affecting the processing of the images to be displayed. Itshould be noted that the processing circuit 115, the display 120, andthe input devices 125 may be part of a unitary system or may be adistributed system with the processing circuit 115, for example, beingseparate and communicatively coupled to the display 120 and inputdevices 125. In some embodiments, servers store the images and clientsrequest and receive the images from the servers, with image processingperformed on the server or on the client, or both.

A plurality of scans may be performed, and analyzed together. Forexample, a first scan of an object (e.g., a patient) may be performedbefore the contrast agent is injected, and several subsequent scans ofthe object may be performed at various times (e.g., at regularintervals) after injection of the contrast agent, as the concentrationof contrast agent changes. The rate at which the concentration ofcontrast agent increases initially, the peak concentration reached, andthe rate at which the concentration of contrast agent subsequentlydecreases all may depend on the type of tissue into which the contrastagent is injected or which is of interest. In some embodiments, thethree-dimensional scan data arrays that result from several scans,performed at different intervals after the injection of the contrastagent, may be processed together e.g., subtracted from each otherpairwise, to form further three-dimensional scan data arrays. Thesearrays may then be analyzed, as described herein, e.g., contours andsurfaces may be generated based on the three-dimensional scan dataarrays, and the contours may be displayed, overlaid on slices (e.g., ontwo-dimensional data arrays composed of elements selected from thethree-dimensional scan data arrays).

As used herein, a “slice” is a two-dimensional scan data array formedalong a surface within a three-dimensional scan data array. For example,for a three-dimensional scan data array for a patient, three axes may bedefined, an “axial” axis (e.g., parallel to a longitudinal direction ofthe patient), a “coronal” axis (e.g., an axis parallel to the front-reardirection in the patient) and a “sagittal” axis (e.g., an axis parallelto a left-right direction in the patient). Planes, and slices, may thenbe defined, with corresponding names, perpendicular to the respectiveaxes. For example, an axial slice may be a two-dimensional subarrayperpendicular to the axial axis, e.g., consisting of all of the elementsof the three-dimensional scan data array at a certain position along theaxial axis. The elements of a slice may also be referred to as “pixels”.The terms “axial”, “sagittal” and “coronal” are not limited, as usedherein, to being parallel to the longitudinal direction of the patient,the left-right direction in the patient, and the front-rear direction inthe patient respectively; instead these terms may refer to anysubstantially orthogonal directions (e.g., three directions, any pair ofwhich is within 15 degrees of being perpendicular).

The three-dimensional scan data array generated by a medical imagingscan may include portions or features not relevant for the subsequentanalysis to be performed. For example, if a medical imaging scan isbeing performed to check for, or characterize, a lesion (e.g., acancerous lesion) within the torso of a patient, then the arms of thepatient, or the buckle of a belt worn by the patient, may be present inthe three-dimensional scan data array. Such features may interfere withsubsequent analysis, and as such, it may be advantageous to excludethem. As such, in some embodiments, a torso contour (a contour thatapproximates the boundary of a patient's torso) may be generated in oneor more slices, and elements of the three-dimensional scan data arraythat fall outside of the torso contour (or outside a rectanglecontaining the torso contour) may be disregarded.

In some embodiments, the generating of the torso contour may proceed asfollows. Within a scan volume consisting of a set of consecutive axialslices (e.g., a set of slices corresponding approximately to a certainportion of the patient, e.g., the portion of the torso below thediaphragm), a central slice may be selected, and within the centralslice, a central row and a central column may be selected. As usedherein, “central” means within the middle one-third, e.g., for a set of30 slices, a central slice is one selected from the range extending fromthe 10^(th) slice to the 20^(th) slice. A plurality of maximum valuesmay then be calculated, each of the maximum values being the maximumvalue within a respective slice of the set of consecutive axial slices.The median of these maximum values may then be used to set a threshold(e.g., the threshold may be set to be equal to a constant factor timesthe median).

Within the central slice, a first rectangle may then be defined, basedon the threshold. The first rectangle may have a left edge at the firstpeak, in order, of two or more horizontal peaks exceeding the thresholdin the central row. As used herein, “first . . . in order” refers to thefirst element in an ordered set of elements, and “last . . . in order”refers to the last element in an ordered set of elements. For example,the first element of an array of N elements may be referred to as thefirst element, in order, of the array, and the N^(th) element may bereferred to as the last element, in order, of the array. When usedwithout the qualifying phrase “in order”, the modifier “first” is usedherein only to distinguish an element from other similar elements, whichmay be referred to as “second”, “third”, and the like, and which mayfollow or precede the first element, if the elements are ordered. Asused herein, a “peak” is a local maximum, i.e., an element having asmaller neighbor on each side. A “horizontal peak” is a local maximum ina row, and a “vertical peak” is a local maximum in a column.

The first rectangle may further have a right edge at the last peak, inorder, of the two or more horizontal peaks exceeding the threshold inthe central role. It may also have a top edge at a first peak, in order,of two or more vertical peaks exceeding the threshold in the centralcolumn, and a bottom edge at the last peak, in order, of the two or morevertical peaks. The first rectangle may then be used to adjust thethreshold, as follows. First, a second plurality of maximum values maybe calculated over the set of slices, each maximum value being themaximum value within the first rectangle in the respective slice, of theset of slices. The adjusted threshold may then be used to generate thetorso contour, by finding a region of the central slice within which thevalues exceed the second threshold, and defining the torso contour to bethe boundary of this region (or the boundary of the largest such region,if there are several). FIG. 2 shows an example of a torso contour 205,in a slice that also contains the patients arms 210. In the example ofFIG. 2, the arms are smaller than the torso and therefore neither arm isidentified as the torso.

Some scan data, such as computerized tomography scan data, may includeother artifacts that may be removed, as follows, before generating thetorso contour. Such artifacts, may be caused, for example, by thepresence of a table supporting the patient during the scan; such a tablemay have a sheet metal upper surface, for example, that may appear as awhite (high density) line in an image of a slice from the scan. In someembodiments, the removal of such artifacts proceeds as follows. First ahorizontal moving sum is calculated along the central row, and ananalogous, vertical, moving sum is calculated along the central column.The width of the filter used for the moving sums may be selected to becomparable to or wider than a characteristic thickness of the artifactsto be removed, e.g., the thickness of the sheet metal upper surface ofthe table.

A rectangle, to be used as a mask, may then be defined, based on apreset threshold. The rectangle may have a left edge, at a first value,in order, within the horizontal moving sum, exceeding the threshold; aright edge, at the last value, in order, within the horizontal movingsum, exceeding the threshold; a top edge, at a first value, in order,within the vertical moving sum, exceeding the threshold; and a bottomedge, at the last value, in order, within the vertical moving sum,exceeding the third threshold. The rectangle may then (as mentionedabove) be used as a mask, and the torso contour may be drawn entirelywithin the second rectangle, thereby avoiding inclusion of artifacts. Inaddition to making possible the exclusion of features (e.g., arms or atable) outside of the patient's torso, the finding of a torso contourmay be helpful for determining the size of the patient. This size may beused to apply suitable scaling, in methods, discussed below, fordetermining the contour of a lesion. As used herein, unless otherwisespecified (as in the phrase “torso contour”), a “contour” refers to acandidate contour corresponding to the boundary, in a slice, of a lesionor suspected lesion.

Contours may be generated around areas suspected of containing lesionsaround a target point, as follows. The target point may be a pixel(selected by the user, as a point within a suspected lesion) in areference slice (which may also be selected by the user, e.g., bystepping through the slices as they are each displayed in sequence).

A suspected lesion may include tissue that is of higher density than thesurrounding tissue, or it may include tissue that is of lower densitythan surrounding tissue. Contours around both types of lesion may bedrawn, by first calculating an outward slope. As used herein, an outwardslope is a measure that returns a positive value at a local minimum anda negative value at a local maximum. Such a slope may be calculated, atthe target point, as follows. First, an average over a first areacontaining the target point may be calculated. Then, the average over asecond area, larger than the first area, and including the first area(and including the target point), may be calculated. The differencebetween the two averages may then be used to calculate the outward slope(e.g., the outward slope may be the average over the second area minusthe average over the first area). For example, if the average over thesecond area is greater than the average over the first area (as would beexpected if the target point is a local minimum), the outward slope maybe positive. As used herein, an “average” may be a weighted average, ora straight average (i.e., a weighted average in which the weights areall equal to one).

The contour of the lesion in the reference slice may be calculated asthe boundary of a region, within the reference slice, consisting ofpixels that either exceed a first threshold, or are less than the firstthreshold, depending on whether the previously calculated outward slopeis positive or negative. For example, if the previously calculatedoutward slope is greater than zero, then a region of pixels less thanthe first threshold may be used; if the previously calculated outwardslope is less than zero, then a region of pixels greater than the firstthreshold may be used. In this manner, the contour-generating method iscapable of producing a meaningful contour regardless of whether thelesion consists of tissue having higher density, or lower density, thanthe surrounding tissue.

Contours (e.g., candidate lesion contours) may be generated using aniterative approach in which each of (i) the first threshold, (ii) athreshold-finding area and (iii) a search area is incrementally adjustedover a number of iterations, each iteration generating an additionalcandidate contour. A user may then view the candidate contours andselect one that, in the user's opinion, is the best fit to the probableboundary of the lesion.

The threshold-finding area and the search area may each be initializedto a preset area around the target point (e.g., the threshold-findingarea may be initialized to a rectangular area centered on the targetpoint, and the search area may be initialized to an elliptical areacentered on the target point). The size of the preset area may be scaledto the size of the patient, based on the finding of a torso contour, asmentioned above. The threshold may then be calculated as a statistic(e.g., an average) over the threshold-finding area, and used to generateone or more contours (each being a boundary of a region within which thescan data values exceed the threshold (for a high-density lesion) orfall below the threshold (for a low-density lesion)). The boundaryincluding the target point (or the boundary enclosing the largest area,if no boundary includes the target point) may then be saved as acandidate contour, and one or both of the threshold-finding area and thesearch area may be increased (e.g., by an amount based on the size ofthe smallest rectangle including all of the contours found for thepresent threshold value), in preparation for generating the nextcontour. This process may be repeated multiple times, with, in eachiteration, the updated threshold being based on the updatedthreshold-finding area. One or more masks may be used, in the process offinding the threshold or in the process of finding contours, to avoidcapturing, within any contour or within the threshold-finding data,regions (e.g., regions outside the patient) that are not candidates forcontaining lesions.

In some embodiments, the changing of the threshold is stopped or limitedafter a fixed number of iterations (e.g., after two iterations) or afterthe threshold has been changed during a certain number of previousiterations. For example, when the threshold was adjusted both on theprevious iteration, and on the iteration preceding the previousiteration, a flag (which may be referred to as a “freeze flag”) may beset. When the freeze flag is set (e.g., on subsequent iterations), thethreshold-finding area may be left unchanged, and the threshold may bechanged by a fixed amount (e.g., by a fraction of (e.g., 20% of) theamount by which the threshold was changed on a previous iteration, whenthe freeze flag was not set). The use of a freeze flag may avoid asituation in which the contours grow to enclose large amounts of normaltissue outside of the lesion.

The contours may then be displayed (e.g., simultaneously, or one at atime) to a user, who, as mentioned above, may select a contour that, inthe user's opinion, is the best fit to the probable boundary of thelesion. The threshold corresponding to this contour, the sign of theoutward slope, and the centroid of the area enclosed by the centroid,may be saved for use in finding a contour in an adjacent slice, asdiscussed in further detail below.

A contour may then be found in an adjacent slice, by finding theboundary of a region, within a search area in the adjacent slice,consisting of pixels that either exceed the first threshold, or are lessthan the first threshold, depending on whether the previously calculatedoutward slope is negative or positive, respectively (i.e., whether thelesion is a high-density lesion or a low-density lesion, respectively).The search area may be an area (e.g., an elliptical area) containing(e.g., centered on) the centroid of the reference slice. This processmay be repeated on further slices (e.g., on a slice adjacent to theslice adjacent to the reference slice), each time using the centroid ofthe area enclosed by the contour in one slice as the target point (forselecting the search area) in an adjacent slice. The process may berepeated for all of the slices of interest on one side of the referenceslice (e.g., all of the slices of interest above (i.e., nearer to thehead of the patient than) the reference slice), and the process may alsobe repeated for all of the slices of interest on the other side of thereference slice (e.g., nearer to the feet of the patient than thereference slice). A plurality of respective contours, in a contiguousset of slices, may then define a surface of the volume of the lesion(e.g., each of the plurality of contours may be in the surface of thevolume of the lesion).

The methods described herein may be used for a plurality of lesions,e.g., each identified by the user by designating a respective targetpoint in the reference slice. For example, a plurality of first axialcontours may be generated, for each of a first plurality of axialslices, the plurality of first axial contours defining a first volume(the volume of a first lesion), and a plurality of second axial contoursmay be generated, for each of a second plurality of axial slices (whichmay be the same as the first plurality of axial slices), the pluralityof second axial contours defining a second volume (the volume of asecond lesion). The contour of the first volume and the contour of thesecond volume may then be calculated in another slice (e.g., a sagittalslice) and displayed, overlaid on the sagittal slice. FIG. 3A shows anaxial slice in which a first contour 305, showing the boundary of afirst lesion, and a second contour 310, showing the boundary of a secondlesion, have been overlaid on an image of the slice. In someembodiments, contours around the same lesions may be shown in other(e.g., orthogonal) slices, annotated or color-coded to identify thecorrespondence between the contours in the axial slice and the contoursin the perpendicular slice. For example, FIG. 3B shows a sagittal view,for a sagittal slice passing through the target point of the referenceslice, showing the same two lesions as those of FIG. 3A, with a firstsagittal contour 315 being on the surface of the volume of the firstlesion, and a second sagittal contour 320 being on the surface of thevolume of the second lesion. The correspondence between the contours inFIG. 3B and those in FIG. 3A may be indicated by the color of thecontours in FIG. 3B; for example, the first contour 315 in FIG. 3B maybe displayed in yellow, and the second contour 320 may be displayed incyan. An analogous coronal view may be generated and displayed in asimilar manner. Such a view may show a coronal slice passing through thetarget point of the reference slice, and, overlaid on the image of thecoronal slice, contours of the same two lesions as those of FIG. 3A,with a first coronal contour being on the surface of the volume of thefirst lesion, and a second coronal contour being on the surface of thevolume of the second lesion.

As used herein, “a portion of” something means “at least some of” thething, and as such may mean less than all of, or all of, the thing. Assuch, “a portion of” a thing includes the entire thing as a specialcase, i.e., the entire thing is an example of a portion of the thing. Asused herein, the term “rectangle” includes a square as a special case,i.e., a square is an example of a rectangle, and the term “rectangular”encompasses the adjective “square”. As used herein, when a second numberis “within Y%” of a first number, it means that the second number is atleast (1−Y/100) times the first number and the second number is at most(1+Y/100) times the first number. As used herein, the word “or” isinclusive, so that, for example, “A or B” means any one of (i) A, (ii)B, and (iii) A and B. As used herein, the term “array” refers to anordered set of numbers regardless of how stored (e.g., whether stored inconsecutive memory locations, or in a linked list).

The term “processing circuit” is used herein to mean any combination ofhardware, firmware, and software, employed to process data or digitalsignals. Processing circuit hardware may include, for example,application specific integrated circuits (ASICs), general purpose orspecial purpose central processing units (CPUs), digital signalprocessors (DSPs), graphics processing units (GPUs), and programmablelogic devices such as field programmable gate arrays (FPGAs). In aprocessing circuit, as used herein, each function is performed either byhardware configured, i.e., hard-wired, to perform that function, or bymore general-purpose hardware, such as a CPU, configured to executeinstructions stored in a non-transitory storage medium. A processingcircuit may be fabricated on a single printed circuit board (PCB) ordistributed over several interconnected PCBs. A processing circuit maycontain other processing circuits; for example, a processing circuit mayinclude two processing circuits, an FPGA and a CPU, interconnected on aPCB.

As used herein, when a method (e.g., an adjustment) or a first quantity(e.g., a first variable) is referred to as being “based on” a secondquantity (e.g., a second variable) it means that the second quantity isan input to the method or influences the first quantity, e.g., thesecond quantity may be an input (e.g., the only input, or one of severalinputs) to a function that calculates the first quantity, or the firstquantity may be equal to the second quantity, or the first quantity maybe the same as (e.g., stored at the same location or locations in memoryas) the second quantity.

Although limited embodiments of a system and method for generating anddisplaying contours have been specifically described and illustratedherein, many modifications and variations will be apparent to thoseskilled in the art. Accordingly, it is to be understood that a systemand method for generating and displaying contours employed according toprinciples of this disclosure may be embodied other than as specificallydescribed herein. The disclosure is also defined in the followingclaims, and equivalents thereof.

What is claimed is:
 1. A method for analyzing scan data, the methodcomprising: generating a respective first axial contour, of a pluralityof first axial contours, for each of a first plurality of axial slices,the first axial contours defining a surface of a first volume, a firstaxial slice of the first plurality of axial slices including a firsttarget point; generating a first sagittal contour in a first sagittalslice through the first target point, the first sagittal contour beingin the surface of the first volume; generating a respective second axialcontour, of a plurality of second axial contours, for each of a secondplurality of axial slices including the first axial slice, the secondaxial contours defining a surface of a second volume, a first slice ofthe first plurality of axial slices including a second target point; andgenerating a second sagittal contour in the first sagittal slice, thesecond sagittal contour being in the surface of the second volume. 2.The method of claim 1, further comprising displaying: the first axialslice; the first axial contour of the first axial slice, overlaid on thefirst axial slice; the second axial contour of the first axial slice,overlaid on the first axial slice; the first sagittal slice; the firstsagittal contour, overlaid on the first sagittal slice; and the secondsagittal contour, overlaid on the first sagittal slice.
 3. The method ofclaim 2, wherein the displaying of the first sagittal slice, the firstsagittal contour, and the second sagittal contour comprises: displayingthe first sagittal contour in a first color, and displaying the secondsagittal contour in a second color, different from the first color. 4.The method of claim 1, further comprising generating a torso contour inthe first axial slice, the first axial slice being a slice of an imagingscan of a patient, the torso contour corresponding to the boundary, inthe first axial slice, of the torso of the patient.
 5. The method ofclaim 4, wherein the generating of the torso contour comprises:calculating a first plurality of maximum values, each of the maximumvalues being the maximum value within a respective slice of a thirdplurality of axial slices, the third plurality of axial slices includingthe first plurality of axial slices and the second plurality of axialslices; calculating a first threshold based on the median of the maximumvalues; and defining a first rectangle having: a left edge at a firstpeak, in order, of two or more horizontal peaks exceeding the firstthreshold in a central row of a central slice of the third plurality ofaxial slices; a right edge at a last peak, in order, of the two or morehorizontal peaks; a top edge at a first peak, in order, of two or morevertical peaks exceeding the first threshold in a central column of thecentral slice; and a bottom edge at a last peak, in order, of the two ormore vertical peaks.
 6. The method of claim 5, wherein the generating ofthe torso contour further comprises: calculating a second plurality ofmaximum values, each of the second plurality of maximum values being themaximum value within the first rectangle in a respective slice of thethird plurality of axial slices, and calculating a second thresholdbased on the median of the second plurality of maximum values.
 7. Themethod of claim 6, wherein the generating of the torso contour furthercomprises finding a boundary of a region exceeding the second threshold.8. The method of claim 7, wherein: the scan data is computerizedtomography scan data; the generating of the torso contour furthercomprises: calculating a horizontal moving sum along the central row;calculating a vertical moving sum along the central column; and defininga second rectangle having: a left edge at a first value, in order, ofthe horizontal moving sum, exceeding a third threshold; a right edge ata last value, in order, of the horizontal moving sum, exceeding thethird threshold; a top edge at a first value, in order, of the verticalmoving sum, exceeding the third threshold; and a bottom edge at a lastvalue, in order, of the vertical moving sum, exceeding the thirdthreshold; and the region is within the second rectangle.
 9. Anon-transitory computer readable medium, the non-transitory computerreadable medium storing instructions that, when executed by a processingcircuit, cause the processing circuit to: generate a respective firstaxial contour, of a plurality of first axial contours, for each of afirst plurality of axial slices, the first axial contours defining asurface of a first volume, a first axial slice of the first plurality ofaxial slices including a first target point; generate a first sagittalcontour in a first sagittal slice through the first target point, thefirst sagittal contour being in the surface of the first volume;generate a respective second axial contour, of a plurality of secondaxial contours, for each of a second plurality of axial slices includingthe first axial slice, the second axial contours defining a surface of asecond volume, a first slice of the first plurality of axial slicesincluding a second target point; and generate a second sagittal contourin the first sagittal slice, the second sagittal contour being in thesurface of the second volume.
 10. The non-transitory computer readablemedium of claim 9, wherein the instructions further cause the processingcircuit to display: the first axial slice; the first axial contour ofthe first axial slice, overlaid on the first axial slice; the secondaxial contour of the first axial slice, overlaid on the first axialslice; the first sagittal slice; the first sagittal contour, overlaid onthe first sagittal slice; and the second sagittal contour, overlaid onthe first sagittal slice.
 11. The non-transitory computer readablemedium of claim 10, wherein the displaying of the first sagittal slice,the first sagittal contour, and the second sagittal contour comprises:displaying the first sagittal contour in a first color, and displayingthe second sagittal contour in a second color, different from the firstcolor.
 12. The non-transitory computer readable medium of claim 9,wherein the instructions further cause the processing circuit togenerate a torso contour in the first axial slice, the first axial slicebeing a slice of an imaging scan of a patient, the torso contourcorresponding to the boundary, in the first axial slice, of the torso ofthe patient.
 13. The non-transitory computer readable medium of claim12, wherein the generating of the torso contour comprises: calculating afirst plurality of maximum values, each of the maximum values being themaximum value within a respective slice of a third plurality of axialslices, the third plurality of axial slices including the firstplurality of axial slices and the second plurality of axial slices;calculating a first threshold based on the median of the maximum values;and defining a first rectangle having: a left edge at a first peak, inorder, of two or more horizontal peaks exceeding the first threshold ina central row of a central slice of the third plurality of axial slices;a right edge at a last peak, in order, of the two or more horizontalpeaks; a top edge at a first peak, in order, of two or more verticalpeaks exceeding the first threshold in a central column of the centralslice; and a bottom edge at a last peak, in order, of the two or morevertical peaks.
 14. The non-transitory computer readable medium of claim13, wherein the generating of the torso contour further comprises:calculating a second plurality of maximum values, each of the secondplurality of maximum values being the maximum value within the firstrectangle in a respective slice of the third plurality of axial slices,and calculating a second threshold based on the median of the secondplurality of maximum values.
 15. The non-transitory computer readablemedium of claim 14, wherein the generating of the torso contour furthercomprises finding a boundary of a region exceeding the second threshold.16. The non-transitory computer readable medium of claim 15, wherein:the scan data is computerized tomography scan data; the generating ofthe torso contour further comprises: calculating a horizontal moving sumalong the central row; calculating a vertical moving sum along thecentral column; and defining a second rectangle having: a left edge at afirst value, in order, of the horizontal moving sum, exceeding a thirdthreshold; a right edge at a last value, in order, of the horizontalmoving sum, exceeding the third threshold; a top edge at a first value,in order, of the vertical moving sum, exceeding the third threshold; anda bottom edge at a last value, in order, of the vertical moving sum,exceeding the third threshold; and the region is within the secondrectangle.
 17. A system for generating a view of an interior of anobject, the system comprising: a scanner for scanning the object; aprocessing circuit; and a display, the processing circuit beingconfigured to: generate a respective first axial contour, of a pluralityof first axial contours, for each of a first plurality of axial slices,the first axial contours defining a surface of a first volume, a firstaxial slice of the first plurality of axial slices including a firsttarget point; generate a first sagittal contour in a first sagittalslice through the first target point, the first sagittal contour beingin the surface of the first volume; generate a respective second axialcontour, of a plurality of second axial contours, for each of a secondplurality of axial slices including the first axial slice, the secondaxial contours defining a surface of a second volume, a first slice ofthe first plurality of axial slices including a second target point; andgenerate a second sagittal contour in the first sagittal slice, thesecond sagittal contour being in the surface of the second volume. 18.The system of claim 17, wherein the processing circuit is furtherconfigured to display: the first axial slice; the first axial contour ofthe first axial slice, overlaid on the first axial slice; the secondaxial contour of the first axial slice, overlaid on the first axialslice; the first sagittal slice; the first sagittal contour, overlaid onthe first sagittal slice; and the second sagittal contour, overlaid onthe first sagittal slice.
 19. The system of claim 18, wherein thedisplaying of the first sagittal slice; the first sagittal contour; andthe second sagittal contour comprises: displaying the first sagittalcontour in a first color, and displaying the second sagittal contour ina second color, different from the first color.
 20. The system of claim17, wherein the processing circuit is further configured to generate atorso contour in the first axial slice, the first axial slice being aslice of an imaging scan of a patient, the torso contour correspondingto the boundary, in the first axial slice, of the torso of the patient.